The nos monster was a carnivorous reptile native to the sinkholes of Utapau. Residing in the dank grottos deep underground, the aquatic nos' wide eyes were accustomed to the dark. Fiercely protective of its young, the nos would attack any threat it perceived.

The varactyl and the nos may have shared an ancient evolutionary ancestor as both were native to the same world, and shared similarities between the two. Additionally, the nos monster was closely related to the swamp slugs of Dagobah.

Obi-Wan speculates briefly that the nos may have been a distant "cousin" of sorts to the varactyl, spotting similarities between the two beasts, in the Revenge of the Sith novelization.

A scene in which Obi-Wan Kenobi encounters a nos monster was cut from the final release of Revenge of the Sith. It would have been as follows:

After being forced deep into the underground caves below Pau City, Obi-Wan Kenobi happens upon a female nos monster and her young. While the Jedi Master manages to stay hidden, the two seeker droids that follow him are not so lucky. One is destroyed with a single chomp of the nos monster's jaws, while the second is chased from the cave by the angry nos. Obi-Wan passes by the monster's nest without harming the agitated babies.

The image Who's the Noss? on SW.com is an incorrect way of spelling the monster's name.